Acpi ???

I have Xp pro and somtimes it can power down my system and sometime it cant WHY????

why is it able to shut down fine one day then the other i have to hit the power button

It can depend on loads of things - which OS\apps were you running, which hardware&drivers do you have installed; is there a LAN, etc... Please tell more about your rig - maybe we'll be able to help...

look in the driver details for the acpi, in the divice manager, and see if the hal.dll is there. if not, you'll have to run the sfc and get it from the xp disc. the hal.dll is the driver that makes the xp do the shutdown.